For a month or two now, one of my '00 LeSabre'* engine pulleys has been making a high-pitched whining noise that comes and goes when the engine is running. It'* one of those "gee I should get that checked out" sorta thing, but never got around to it yet. Last night while driving, that noise suddenly became a loud metallic whirring... as if I'm swirling/spinning some ball bearings around in a metal cup (best way I can describe the noise).

All the engine pulleys are still spinning and the engine itself is running fine... but with those horrible metallic noise. I'm really not familiar with how these pulleys are connected or where the obvious failure could be. What am I looking at here? Is the car safe to drive to a repair shop, or am I risking engine damage of some kind?

If it comes and goes, most likely would be the A/C clutch.....

With the car running, observe the clutch, and have someone turn the A/C on/off, repeatedly, pausing between on/offs.....see/hear if the noise occurs...remember, A/C comes on in defrost mode.....

couple things yo could do to narrow it down. see if it changes with or without the a/c on. and take the belt off and spin the different pulleys, alot of times when it gets bad you can hear or feel the bad one by spinning by hand

I was wrong... the pulleys are NOT all spinning. I couldn't them clearly last night in teh dark when I noticed the noise. Looking at the engine sideways (imagine the pulleys in "front" of you), the one on the bottom right corner is partially seized up and only turning slowly while the others are spinning rapidly. The noise is massive belt slipping, although it sure sounded like metal-on-metal.

The seized pulley appears to be the A/C compressor, so 2 questions...

(1) Does the entire compressor have to be replaced, system flushed, etc.? Or can the pulley (or whatever part failed) just be replaced?

(2) Can the A/C be bypassed for this upcoming winter, so at least I won't have to mess with this for 4-5 months?

I don't think the pulley is seized......what is happening is, the clutch is partially catching the pulley.......

With the engine off(not running), you should be able to grab the clutch plate(not the pulley) and rotate it....this tells you if the compressor is not seized......if it isn't, then the clutch plate either doesn't have enough clearance or over time rust/dirt has built up in the gap between the pulley and clutch plate so there is partial contact......what you can do, is create a bigger gap(special tool), and this will eliminate the plate grabbing the pulley, and eliminate the noise for the winter.....then in the spring, you must decide whether to replace the clutch plate, clutch plate and pulley(if needed), or the whole compressor......one possible problem is, when the defroster is commanded, if the compressor is commanded on(pressure is high enough), it may pull that plate in enough to make partial contact and create noise......so, once you have sufficient gap, disable compressor by removing harness from it(taping it up real good, and also the connector on compressor), or removing the A/C clutch relay.....

I agree^^

To answer your 2 question the ac can be by passed by taking it of off
and getting one of these at most auto parts store.

About $25 to $35 dollars

This could be a 2 choice if the the clutch ac bearing is messed up
pulling the fuse or relay wont help the

Hope this helps relay or fuse pull.

I would try first as Teck 2 said

Good call and this is indeed the case. Let me clarify that although I can turn the clutch plate, it doesn't spin freely or anything (not sure if it'* supposed to). But I can crank it around with my hand.

What is the special tool called and where do you suggest I obtain one? I wonder if it'* a rental item (i.e. free to use) at Advance Auto or the like.

What'* that thing called, and how does it attach and keep that pulley in the belt path? It almost seems like that would require the compressor to be removed first.

Oh and one more thing... there are what appear to be "fresh" (shiny silver) metal shavings stuck to the inner side of the outer clutch plate. See photo below, which is a straight-down shot of the compressor pulley. In case that changes anything, as I know failed/seized compressors can deliver metal shavings into the A/C system. The shavings are stuck on there because they appear to be magnetized.

Your ac clutch bearing has failed it wont affect the compressor
basic you have 3 choices get a new or rebuilt hub assembly
or bearing {but its staked inside the clutch hub }
That makes removal not so easy and most time the hub
will be worn

Or you can get a compressor assembly throw it on for now
remove the ac relay or ac fuse for now
then come spring get a new dryer
and have the ac recharged

NOTE replacing the hub assembly can be done on the car BUT
it requires special tools {rental from most auto parts stores}
and can require you to drop the sub frame down to get at the
front of the compressor.

On one side with a jack
the only plus doing it on the car is you don't loose the AC charge

It would be the easiest replacing the compressor as a assembly
if time is a factor

The last option would be taking the compressor off and
replacing the compressor with the pulley assembly
with a

Replacement A/C Compressor By-Pass Pulley

lowest cost would be the A/C Compressor By-Pass Pulley